Temperature responsive electric switch



l. E. MCCABE May ll, 1943.

l t e kan uw t e e .n S H2 C T I w s C M1 T ou El m. ,n E V In w mA. mwnu MF U T A Dn E m E T INVENTOR. /RA E. MC CABE A T'VORNE Y.

May ll, 1943. l. E. MCCABE 2,318,699

TEMPERATURE RESPONSIVE ELECTRIC SWITCH Filed April 14. 1941 2sheets-sheet 2 28 27 AQ' gmx@ 4 INVENTOR. /RA E. Mccn/L' ATTORN E YPatented May 11, '1943 'rmanama nasrouslva ELECTRIC swrrcn Ira E.McCabe, Chicago, Ill. Application April 14, 1941, semi No. sss,4z4

(ci. zoo-13s) 9 Claims.

This invention relates. to improvements in electric switch mechanismsand more particularly to the structure of temperature responsiveelectric switches. 1

It is an object of this invention to provide a switch of the characterdescribed'and. illustrated in this applicants rprior Patent No.

1,834,288, dated December 1, 1931, wherein the parts are so constructedthat compensating adjustments may be made at the factory to insureconsistent manual adjustments in the eld. Electric switches of this typeare designed to control the operation of domestic heating systems, aswell as for industrial purposes with some of the more common uses beingto limit temperature within furnaces, bake ovens, 'stack pipes and ductsand for the control of dampers and circulating fans employed in warm airheatingsystems. Devices of this character when installed in connectionwith electrically operated and controlled heating systems have thethermally responsive element extending into the stack or pipe leadingfrom the furnace or heater to the chimney or into the bonnet if theheater is a warm air furnace or in warm air ducts running from thefurnace, withV the instrument or switch casing supported on the exteriorthereof.

Because of the various temperatures at which the device may be desiredto operate due to the variety of uses to whch it may be put and itslocation when installed, it is desirable for such a device to be madeoperable over a wide temperature range and adjustable over that range inVsuch a manner as will permit the adjustment oi the high and lowoperating points independently of each other. Furthermore .when suchdevices are applied to domestic heating apparatus, the compact andimproved appearance of the heating plants being made today necessitateor make desirable the use of controlling devices, attached thereto, tobe small and compact'to fit into limited space and to harmonize limitedmovement of the. temperature responsive actuating means beyond thepredetermined adjusted temperatures which limit the opera- I tion of theswitch thus protecting the temperawith the general design of the newtype of boilers and furnaces. It is also'desirable that when thesedev'ices are of the adjustable type that the adjustments be made uponthe exterior of the enclosure for the operating instrumentality.

It -is thus an object of this "invention to provide a small and compacttemperature actuated switch of the character and for the uses describedin which a simple form of adjusting means permits the adjustment of theoperating points to be made upon the exterior of the switch enclosure.It is a further object to provide a switch operating structurepermitting unture responsive means and preserving the calibration of thedevice. It issti11 'a further object to provide means to compensate forvariations in the manufacture of helical bi-metallic coils employed asthe temperature responsive actuating means, when calibrating the devicefor service. Still another object resides in the lprovision of amanually operated locking means for locking the switch in closedposition, in those forms of devices which open the switch on fallingtemperature, and to automatically release the locking means when thetemperature has risen above the low setting of the device sufllcientlyto maintain the switch closed while temperature remains above the lowsetting.

With these and other objects in view reference is made totheaccompanying sheets. of drawings illustrating a preferred form of thisinvention with the understanding that minor changes may be made withoutdeparting from the scope thereof.

In the drawings:

Figure 1 is a view in side elevation of a preferred form of thisinvention with parts broken away illustrating the' adjusting andoperating mechanism in elevation.

Figure 2 is a front view of Figure 1 with the front cover removed.

Figure 3 'is an enlarged fragmentary detail view in vertical sectiontaken on the line 3 3, Figure 2, illustrating some parts in elevation.

l Figure 4 is a detail view in perspective of parts of the switchoperating mechanism as connected to the operating shaft. s

Figure 5 is a detail view in perspective illustrating the means ofadjustment between the operating shaft and parts actuated thereby.

Figure 6 .is a detail view in elevation, with parts brolnen away,illustrating the position assumed by the parts when the 'thermal elementin response -to temperature changes has oscil` ing the positions ofthetoothedwheel adjacent the disk in dot and dash lines.

Figure 11 is a detail View in elevation illustrating the' stop 0nl theswitch carrier arm and notch on the underside of the front plate tolimit the travel of the said arm, showing the position assumed at oneend of travel in full lines and at the other end of travel in dot anddash lines.

Figure 12 is a View similar to Figure 11 illustrating the lock .latch inengagement with the stop on the switch carrying arm in full lines andthe position of the lock latch when disengaged in dot and dash lines.

In the embodiment of this invention illustrated upon the accompanyingsheets of drawings,

the thermally responsive element is shown in Figure 1, as a helical coilI of bi-metallic metal,

one end of which is secured to a cylindrical tube 2 adapted to beinserted -through the stack or casing of a furnace or heater employingan electrically operated and controlled fuel burning mechanism. The tube2 is preferably held in position in the stack or casing by an adjustableclamp member 3. The exterior end of the tube 2 is rigidly secured to Theouter or free end of the thermal coil I is rigidly secured to the end ofan operating shaft 5 which passes through the tube 2 and an opening 6provided therefor in the rear wall of the casing 4 and is terminatedadjacent thereto. As shown in Figure 3, the inner end of the operatingshaft 5 is rotatably received in a bearing 1 therefor mounted on asupporting plate 8 extending transversely of the casing 4 and held inspaced apart relation by posts 9 in engagement with the The bearing Ibeyond the end of the operating shaft 5 provides a bearing for a reducedaxial stub of aswitch arm carrier member I `having a similar reducedaxial stub on its other end rotatably received in a recessed rear wallthereof.

bearing stud II extending in line with the axis d of the operating shaft'from a front plate I2 spaced apart in parallel relation to thesupporting plate 8 by extensions I3 of the posts 9.

An inverted U-shaped switch operating bracket v I4 Ais perforatedadjacent the free ends of each arm so that the bracket may be mounted tooscillate about the bearing II on the front `plate I2 and the operatingshaft 5, The' switch operating bracket is oscillated by the movementofthe op- .erating shaft in response to the contraction and expansion ofthe thermal element in response to temperature changes. To transmit;Lthe motion of the operating shaft 5 to the Voperating bracket, a-.diskI5 is keyed on the shaft. An actuating arm I 6, rotatably mounted on theshai t 5, of greater length than the diameter of the disk so that eachend projects beyond the periphery of the disk, is provided at its lowerend, with an adjustable clamping member I1 which is adapted to engagethe diskto cause the arm to rotate with the disk, as -shown in detail inFigure 5: As shown in Figure 4, the upper free end of the arm IB.projects between two arms I8 and I9 exthe rear wall 'and supports thecasing 4 enclosing the switch mechanism.

tending `upwardly from separate disks and 2| 26 4extensions 22 and 23.the type No. 1,757,436, dated May 6, 1930, which closes the mounted torotate on the shaft 5 on the side of the arm of the bracket I4 oppositethe actuator arm I6. The free ends of these arms are bent rearwardly sothat they will engage opposite sides of the bracket I4 and extend in thepath of the free end of the actuating armv I 6. The disks 20 and 2I areeach provided with angular the ends of which are bent in the directionof the front of the casing 4 and act asjanchorsv for the opposite endsof a coil spring 24 which is passed over a. grooved hub 25 rotatablymounted on the shaft 5 so as to exert tension on the arms I8 and them inengagement with the opposite sides of the bracket I4 and arm I6.

'I'he switch operated by the oscillation of the bracket I4 is a mercurytube switch, preferably of disclosed in this applicants prior Patentcircuit when tilted above its transverse axis in one direction and whichopens the circuit when tilted in the opposite direction. The mercurytube switch 26 is secured between clamps 21 mounted upon the upper rightangular extension 2'Ia of the switch carrier arm 28 mounted upon theswitch arm carrier I0. 'I'he arm 28 extends therebelow and is terminatedin a right angular extension 29. An actuator stud is mounted on the arm28 below the carrier member l0 and extends below the front plate I2 tobe received in a notch 3| formed in the lower surface thereof so thatthe ends of the notch being engaged by the stud 30 limit the amount ofoscillation imparted to the carrier arm 28. The carrier arm 28 is alsoprovided with an oppositely extending stud 32 above the carrier memberI0 which is engaged with a plate 33 mounted on the carrier member I thelower end of which is engaged by the free end of the extension 29 ofthe'arm 28.

The outer arm of the oscillating operating bracket I4 adjacent. its topis provided with an outstanding pin 34 which acts as a pivot for theupper end of an operating latch 35 which extends downwardly therefrom toa point adjacent the upper surface of the front plate I2 and then isprovided with a hooked lower end, as shown in Figure 4. The operatinglatch 35 mounts an outstanding post 36 extending beyond the uppersurface of the front plate I2. The hooked shaped lower end of theoperating latch 35 is so formed that it includes a. l horizontal slot 31opening therefrom and a,vertical slot 38 which provides means forslidably receiving the actuator st ud 30 upon the switch operatingbracket I4. The horlzontal slot 3'1A allows the end of the latch 35 toswing, `without engagement, about the bearing post II on the front plateI2. From the structure thus described itis apparent that with theactuating arm I6 properly clamped to the disk I5.

movement imparted to the disk I5 by the shaft 5 will in turn cause the`rotation of theV bracket I4. As the bracket is caused to move from leftto right the operating latch 35 is oscillated, with its lower hooked-extremity rotating around the switch actuator stud 30, extendingthrough the slot '38, without moving the stud.

To cause movement of the 'operating latch 35 to actuate the switch 26,and to determine the temperature at which point operation of the switchoccurs, two adjustable stops are provided, hereinafter described, which,when engaged by the latch post 36, serve as a fulcrum for imparting anoscillating movement to the hooked end. When the post is brought intoengagement with a stop, movement thereaftt; imparted. to the I9 tonormally keep y operating latch J5 will osciilate the hooked end thereoiwhich. through its slotted engagement with stud 30. will actuate theswitch from one position to another. As shown in Figure 8. the operatingshalt has rotated in. one direction to rotate the switch operatingbracket i4 carrying the latch 35 with it until the post 36 thereonengages the lett hand slop. so that iurther rotation in the samedirection causes the mercury switch to be tilted to the left. Whenl theswitch is moved past center it continuesin its movement, by its ownweight. until the stud 30 engages the end of the notch Ji in theunderside or the iront plate i2 which acts as a stop to limit the travelofthe bracket i4 and arm 2l in that direction. as shown in dot and dashline in Figure ll.

Thus a positive action is obtained in opening or closing the switchcircuit. Upon oscillation ot the operating shait 5 in the oppositedirect ion the movement oi the parts are reversed.

The coil spring 24. as shown in Figure 4. maintains the arms i8 and ilnormally in engagement. with the actuator arms IB and the bracket i4 toimpart the oscillating movements oi the operai.-

ing shalt. 5 in response to temperature changes to the bracket i4 ashercinbeiorc described. when the mercury switch has been actuated andthe bracket i4 and arm 2l is restrained trom further movement by thestud Jil engaging one oi the stops. should the temperature continue tochange to cause the thermal coil i to expand or contract beyond thatwhich actuated the switch. the sprlm: 24 allows further continuedmovementy ot the shalt l in one direction. as shown in Figure G. or

in the opposite. direction. as show-n in lFigure 7. :l

without placing undue strain upon the thermal coil or any ol the parts.

The actuating arm ii is adjnstabiv mounted upon the disk i5 secured tothe shaft. 5. so that when calibrating the device compensation can bemade for variations-in the relationship between the mounting holes inthe thermal eoll I. As an alternative arrangement the disk i5. Figure 5.may be omitted and the arm i-G keyedA to the shaft and a suitableadjustable clamp provided upon the exterior end oi shalt 5 inr securingthereto the ouier'end oi the thermal coil no matter what its position. l

One oi the two stops [or post Si is in the iorm oi a toothed disk Il.having an annular slot 40 therein through which the post Ji projects.mounted lor rotation upon an extension oi the bearing member Ii on theiront side oi the iront plate i2. The other is an arm 4I projectingbevond the periphery 0i the disk J9 extended trom a disk mounted lorrotation about the same bearing member ii in iront ot the annular slot.-ieddisk JQ. The arm 4i terminal-s in a pointed indicator 42 and isprovided with a depressed tooth 4J adapted to extend over the peripheryof the toothed disk J9 and beine adapted tor engagement between twoadjacent teeth thereon. The arm 4i is also provided with a bent overstop 44 extending through the annular slot 40 in the disk 3! to be inline with and act as a stop lor the post J6 on the latch 35. The disk Ilis also provided with a radl'ai pointed indicator 45 adjacent the rightend oi the annular sint 40. Both pointed indicators are mounted to bepositioned over an annular' segment 4l secured at its'eneis upon theiront plaie i2 and provided with a calibrated temperature scale overwhich the pointed indicators 42 and 45 may be adjusted,

As shown in Figures 2 and i0. the toothed disk Il ts normally restrainedtrom rotation by a plate or strip 4I having a notch 41 stepped at, bothends to receive a toothed disk n below its horizontal diameter and allowfor rotation ofthe disk when the latter is moved out between the widerportions oi the notch but when moved forward the bottom steps oi thenotch 4i enter between adjacentteethon the disk to hold it in jixedposition. This strip 48 is heid with the notched portions at rightangles and adjacent to the at lace oi the disk 3! by right angularextensions at cach end and perforated to be secured to the ends oi theannular scale 48 by the same means which secures the scale to the frontplate i2. Provision is made to adjust the disk 39 so that the right endoi the annular slot 40 will act, as a stop for the latch stud 3i toactuate the switch at the desired temperature indicated on the scale bythe pointer 45. Also provision is made to adllust the arm 4i so that itsstop 4I will be engaged by thelatch stud 36 to reverse the position oithe switch atthe desired temperature indicated on the scale by theposition oi the pointed indicalor 42.

The means provided tor setting the pointers 42 and 45 at the desiredtemperature includes a recessed hub 40 mounting a superimposed reeessedhub 4! with the hub 4l mounted upon the portions 5U and 5h" oi thebearing member il extending tromthe iront side ol the iront plate I2,Both hubs 4I and 49 extend through an aperture 5i provided thereior inthe cover l2 covering the iront oi the easing 4, as shown in Figure l.As shown in Figure 3 the inner end of the hub 4t mounts and is securedto the toothed disk 39. A coil spring 53 is mounted about the reducedportion Sii'` oi the bearing member il with one end in engagement withthe shoulder 5a on the bearing member and the other in en tlagement withthe shoulder within the opposite end of the recess in the hub 4l. Thisspring normally urges the toothed wheel t) engage the lower steps inth:` notch 41 in the strip 46". The v superimposed hub 4I is alsorecessed and its inner end mounts and is secured to the disk carryingthe arm 4I. The outer circumference of the hub 4l is stepped to ioim asupport adjacent its outer end and adjacent its inner end tor the hub 4!with a space between them for a coil spring 544 received within therecess oi the hub 49 with one end bearing upon the outer step ot the hub4I and another against the bottom 'of the enlarged recess in the hub 4l.to be normally urging the hub 49 and arm 4i to maintain the tooth 43 onthe arm 4i in engagement between ad iacent teeth on the toothed disk 38,The lower step on hub 4l acts as a stop to limit tht` outward movementof the hub 4! against the tension o't the spring 54.

B v means oi thel hubs 44 and 49 projecting through the iront cover 52oi the instrument casing 4. desirable adjustments oi the stops for theoperating latch post 36 may be made aiter installation without removingthe cwer ot the instrument casing. By depressing the hubs 4I and 49.they normally travel in unison. the toothed disk 19 is moved out oiengagement with its retaining plate 45' to allow the pointed indicator45 to be rotated to the temperature on the seale on piate`4l desired. Bypulling out hub 40 the eoil spring 54 will be compressed and allow hub4! to slide over hub 4I to withdraw the tooth 4J on the arm 4i fromengagement with the tooth wheel 3| so that the arm 4i may be rotated tothe desired temperature as indicated on the scale on plate 4l. The coveria provided with a glass covered section for viewing the calibratedplate over which the settings of the two pointers are made.

As shown in the drawings and described. 'the mercury switch IG ismounted to close its circuit when actuated upon an increase in'temperature. Such an arrangement is utilized in a device ot thischaracter for closing a` circuit to a circulatlng fan used inconjunction with automatically controlled vand fired warm air heatingsystems. As in the case of such installations it may be desired tooperate the fan during summer seasons for cooling and ventilatlngpurposes. To utilize this improved device for that purpose thisinvention contemplates to provide manually operated means for moving theswitch to closed position. when desired during the summer. and to lockit in that position to cause a continuous operation of the fan untilreleased manually or, in the event of an operation of the firingmechanism, to release the lock upon a temperature :rise after which the.

device again. becomes automatic in operation in response to temperaturechanges.

As shown in Figures l and l2. a lock latch 55 is mounted at one end uponan operating shaft 56 rotatably mounted between the supporting plates Iand i2 with one end extending beyond front platel i2 with its outer endknurled and of such length as to pass through an aperture providedtherefor in the cover 52 for the casing l. 'l'he latch .5S-is soarranged that its free end may be brought into the path of travel of theactuator stud 30 and the free end is notched at 5l so that when theswitch carrying arm 18 has been osclllated to open theswltch 2B theiatch- 55 may be manually rotated lo bring the notched end 5l intoengagement with the actuator stud Jil and oscillate the switch carryingarm 28 in the opposite' direction to close the switch. against the forceof the thermal coil tending to open the switch. Asl

a result only a part of the fitti movement normally made by the switchto full on position is utllized and the latch is locked into engagementwith the stud 30. When in lliis position. the establishment. of heatwhich will raise the iemperature of the thermal coll to remove its torceagainst the locking means. the switch will automatlcaiiy more to thelimit of its on position whereupon the latch lock 55 by its own weightfalls tree and the device becomes automatic in operation in response totemperature changes.

When this device is employed to limit temperature conditions theposition of the switch is reversed in the support clips 11.

Plates of insulating material 5B are preferably attached to the frontside of the supporting plaie l for supporting binding posts 59 to whichthe ends of the flexible leads G0 and iii from the switch terminals arcattached. as shown in Figure 2. for connection into the controlledcircuits.

What I claim is:

l. A temperature responsive device including at tiltable mercury tubeswitch. an operating shaft, a thermal member for operating the shalt. atiltable bracket. means transmitting movement imiti parted to the shaftlo the bracket. a switch actualor operated by the tiltable bracket,adjustable means lor determining the tint(` oi switch operation andmeans upon liu` switch actuator adapted to abut said adjustable meansw-hen the actuator is operated by the tiltable bracket and uponcontinued movement of the bracket thereafter to cause the actuator totilt the. switch including means to limit the tilt of the switch and themovement of the bracket after operatingthe switch, and yielding meansincorporated in sa'id transmitting means allowing continued movement .ofthe shaft beyond the limited movement of the bracket.

2. A temperature responsive device including a tiltable mercury tubeswitch. an operating shaft.

a coil of thermal metal for operating the shafthavlng means on one endthereof to immovably secure that end and 'means on the other end forconnection upon the shalt, a tiltable bracket. an operative connectionbetween the operating shaft and bracket including means secured upon theoperating shaft. means to adjust the relation between the means securedupon the shaft and the bracket in accordance with the position. atambient temperature. of the end o! the coil connected to the shaft, aswitch actuator operated by the tiltable bracket. adjustable means fordetcrmining the time of switch operation. means upon the switch actuatoradapted to abtit said adjustable means when tite actuator is operated bythe tiltable bracket and upon continued movement of the bracketthereafter to cause the actuator to tilt the switch.

3. The structure of claim 2 including means to limit the tilt of theswitch and movement ofthe bracket after operating the switch. andyielding mcans'incorporated in said transmitting means allowingcontinued movement of the shaft beyond the limited movement of thebracket.

4. In a temperature responsive device having a easing. a tiltablemercury tube .switch and actuating means for tilting thc switch withinthe casing, the combination4 with thermally responsive means [oroperating the actuating means and a calibrated temperature scale, ofAadjustable means cooperating with the actuating means for determiningthe temperature points of switch operation including two hubs o nesuperimposed upon the other. the inner hub mounting a toothed diskhaving a pointer projecting beyond the periphery of the disk, retainingmeans to position the disk adjacent the dial and to engage the teeth 0lthe disk to prevent rotation oi the disk. the outer hub mounting apointer arm having a pawl adapted to engage the teeth on the disk. andmeans yielding to the depression of the hubs to release the toothed whelfrom its retaining means to be rotated to the desired position and byanoutward pull of the outer hub to detach the pointer arm pawl from thetoothed disk to rotate the pointer arm to the desired position.

5. In a temperature responsive device having a casing. a tiltablemercury tube switch and actu- 'ating means for tilting the switch withinthe casing. the combination with thermally responsive means foroperating the actuating means and a calibrated temperature scale. ofadjustable means cooperating with the actuating means lor determiningthe temperature points oi switch operation including two hubs, onesuper-imposed upon the other. the inner iutb mount ing a tooth'ed diskhaving a pointer projecting beyond the periphery of the disk. retainingmeans to position the disk adjacent the dial and to engage the teeth ofthe disk to prevent the rotation of the disk. the outer hub mounting upolitici' ai'i'n having a pawi adapted to engage ilu.l teeth on thediskfa spring normally acting on the outer hub to maintain the pawi inengagement with the V disk teeth and yieidabie to movement of the htibtheretainingmeansandyieldahlleupoumove--mmtofthehubtofreethediskiorrotationof thehub.

0. A temperature responsive electric switchlncludingacasing,amercurytubeswltchand switch operating mechanismmounted within the casing, a .temperatureresponsive coil of thermalmetal mounted exteriorly oi the casing havingtoopenandclosetheswitchsaidmechanismincludlng apivoted switch operatinglatch adapted to be actuated upon movement of the operatingshaft.apostprojectmgfromthefreeend ofthe operating latch, spaced apartstops on each nde ofthelatchpostadaptedtobeengaaedbythe posti to throwthe switch .from one position to another; adjustable means to positionthe stops upon a calibrated temperature scale to throw the switch at thedesired degree oi temperature to which the temperature responsive coilis subjected.saidadjustingmeansinch1dingapost projecting through thefront of the casing for manually adjusting the position of both stops.

1. The of claim 6 wherein said adjllln post is in the form oi' two hubsone superimposed upon the other, with the outer hub mounting within thecasing a pointer arm having a stop. the inner hub extending therebeyondand mmmting a toothed disk having an annularalotthroughwhichthelatchpostandthestoponthepointerarmpassQtheradialedgeofthe slotactingastheotherstopforthelatchpost,a

' pointer projecting beyond the periphery of the`diskadjacenttheradialedgestop.aspring pressed pawl normally the tootheddisk and a tooth struck from the pointer arm tonormallybetweentheteethonsaiddishandmeansyieldingtothedepressionofthehubstoreleasethetoothedwheeiiromthepawltobe rotated to the desired positionand by an outwardpullofthe outerhubtodetachthe pointer arm tooth fromthe diskwheel to rotate they pointer arm to the desired position.

8. A temperature responsive electric switchincludingacasing,amercurytubeswitchand switch operating mechanismmounted within the operating shaft with the inner end of the operatingshaft received in one of the bearings in the supporting plate, aU-shaped operating bracket having its free ends perforated, one toreceive and oscillate about the bearing on the front plate and the otherto receive and oscillate about the end of the operating shaft, a mercurytube switch supported'on theupper end of a Y carrier arm extending froma switch carrier mounted for oscillation between the adjacent perforatedends of the bracket, an operative connection between the operating shaftand an arm ,of the operating bracket, an operating latch pivotallymounted adjacent the top of the other arm of the operating bracket, andan operative connection between the operating latch and switch carryingarm whereby expansionand contraction of the thermal coil impartsoscillation to the operating shaft to operate the switch.

* 9. A temperature responsive device including a tiltable mercury tubeswitch, an operating shaft, a thermal member for operating the shaft,

a tiltable bracket, means transmitting movement imparted to the shaft tothe bracket, a switch actuator operated by the tiltable bracket,adjustable means for determining the time of switch operation Fand meansupon the switch actuator adapted to abut said adjustable means when theactuator is operated by the tiltable bracket and upon-continued movementof the bracket thereafter to cause the actuator to tilt the'switch,including a manually operated latch operable to tilt the switch to oneposition and hold the same in its manually tilted position against theeffort ofthethermalmembertotilttheswitchtothe reverse position u'ntil inresponse to a temperature condition wherein the thermal member no longeropposes the actuation Iof the switch. whereupon the latch falls free',of engagement with the tiltable switch.

IRA E. McCABE.

